Directive microwave antenna



Sept. 20, 1949. c. B. H. FELDMAN DIRECTIVE MICROWAVE ANTENNA 2 sheets-sheet 1 Filed June 5, 1943 INVENTOR c. H FELDMAN BZZ .y ATURNEK Sept. 20, 1949. c. B. H. FELDMAN DIRECTIVE MICROWAVE ANTENNA 2 Sheets-Sheet 2 Filed June 5, 1943 /NVENTOR C. B. H. FELD/WAN y ATTORNEK Patented Sept. 20, 1949 DIRECTIVE MICROWAVE ANTENNA Carl B. H. Feldman, Rumson, -N. J., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 5, 1943, Serial No. 489,740 v 4 Claims.

This invention relates tordirective radio systems and particularly to directive antennas especially adapted for use in centimetric radar systems.

As is known radar and object location systems comprising highly directive antennas and utilizing ultra-short waves (1 to 10 meters) or decimetric waves to 100 centimeters) have been successfully employed in the past. tems conventional antennas, such as dipole arrays associated with parabolic reflectors are ordinarily used. It now appears desirable to employ so-called centimetric waves or microwaves having a wavelength of 1 to 10 centimeters in radar systems for the purpose of securing, for a given size and weight of equipment, greater directivity and a higher degree of scanning resolution. For waves of this length the conventional dipole-reflector arrangements mentioned above are not entirely satisfactoryV and it appears desirable and advantageous to obtain for use with centimetric wavesV more eilicient antennas. Moreover, it is now desired to secure, for use in centimetric radar systems of the searching or mechanical steerable type and of the lobe switching type, centimetric antennas having a higher In these sys-V gain and a more suitable directive characteristic than obtained with antennas heretofore proposed It is a further object of this invention to obtain a highly eflicient radar antenna having narrow electric and magnetic plane lobes and a'high gain.

As used herein, the `term-leaky wave guide of l the first kind refers to a circular or rectangular wave guide having Yone or more antenna slots, usually one, extending parallel to the longitudinal axis of the guide. The term leaky wave guide of the second kind refers to a circular or rectangular Wave guide having a plurality of antenna apertures included in one longitudinal wall and spaced in a direction parallel to the longitudinal axis of the guide. In the cepending application of G. C. Southworth Serial No. 420,747, filed November 28, 1941, now Patent No. 2,405,242, issued on August 6, 1946, Fig. 25, the elements 42 and 4| are leaky guides of the rst and second kinds, respectively. The polarization of the H11 Wave in the leaky rectangular guide of the rst kind is parallel to the guide Wall containing the longitudinal slot and in the leaky (Cl. Z50-33.63)

pendicular to the wall containing the transverse slots..

Also, as used herein, the term go, as applied to' a wave or energy, denotes the incident traveling wave which is propagated from a source toward a load or reective element; and the term return wave or energy designates the traveling wave reflected by the load or element andmoving therefrom towards the source. sitely directed go and return waves combineto produce, under certain conditions, a standing wave. significance as the terms go and return used 4in Patents 2,206,923 and 2,231,602 granted to G. C. Southworth on July 9, 1940, and February l1, 1941, respectively.

-In accordance with one embodiment ofthe invention a transceiver is connected through a waveguide switchand a 'pair of branch-guides to both endsv ofarectangular leaky wave guide antenna ofthe secondY kind. The linear. array' included in a longitudinal-'guide wall and comprising a plurality of transverse antenna aper which may be adjusted. The guides are alter-4 nately energized and lobe switching operation is secured.

The invention will be more fully understood from aV perusal of the following specification taken in conjunction with the drawing on which like reference characters denote elements of similar function and on which:

Fig. 1 is a perspective view of one embodiment ofthe' invention comprising a leaky wave guide of the second kind;

Fig. 2 is a directive diagram used for explain- I ing the operationof the system of Fig. 1 and certain other iigures; i Y

Fig. 3 is a perspective view of a diilerent emv two leakyv bodiment of the invention comprising wave guides ofthe second-kind;

Fig. 4 is a perspectivefview` of a modification' of the system of Fig. 3.

Referring to Fig. 1 reference numeral I denotes a translation device such as a eentimetric The oppo- As so deiined, these terms have the samev transmitter or receiver, or a radar transceiver, and numeral 2 denotes a coaxial line having an outer conductor 3- and an inner conductor 4. Numeral 5 denotes an air-filled metallic main Wave guide into which the end portion 5 of the inner conductor 4 projects, the end portion 6' hereinafter being called an exciter or a pick-up. The exciter or pick-upy element 6' and the guide 5 are connected for utilization of horizontally polarized H11 waves. Numeral 'I denotes an air-` lled wave guide switch of the type disclosed in the .copending application of A.. G.v Fox, Serial No. 422,408, filed December 10, 1941, now Patent No. 2,396,044, issued on March 5,1946, andhavfing the longitudinal partition` 8fandthe twodatuning chambers 9 and I0. The partitionA 8L includes an aperture II and a detunes-or vane I2 which continuously rotates about axis I3 in the manner disclosed in the applicationofA; C. Beck, Serial No. 455,322, led August 19, 1942, now Patent'. No. 22,409,183; issued October 15,; 1946l Each of the.` chambers or cavities-'f 9l andy I is connected to the main guide 5 througha separate aperture I4. Num-malsIii` and I'I- denote a pairl of. branch-Wave guides each lled. with a. material I8 having a dielectricvconstantgreater than unity as,- forV example, polystyrene; and each comprising two sections.y I9 andV 20. Cavities` 9 and I0 are connected respectively to. branch guides I6- and IFI through a. sepa-ratezaper ture2zI. Eachof the loaded branch guide: sections I94 is connectedV to its. associated sectionV 20 at. an. appropriate distance from.v the closed end or transverse wall 22 of section, 20.

to G. C. Southworthk mentioned abovaa The leaky guide 23 isv rectangular; incross-section and Vhas a longitudinal axis 2.4'.` One longitudirlalVv wall 25- contains. a: ,plurality'otf transverse.:

antenna slots orY apertures 2lil spaced long-itu,-V dinally and constituting alinea-r array Z1 having. a horizontal axis; 28. One end. of section I9: ofA branch guide I6 is. connected iso-wave guidean"v tenna 23 at apcint 29 near'theend wall 30 of guide 23 and separated therefromby a quarter wave-length; and one end of section' I9V of` branch guide I'I'is similarly connected to guideI 23A ata point 3:! near'. theV end wall 32v andspaced' therefrom a quarter wavelength; The transverse orY magnetic plane dimension bof guide 23 and the. dielectric .constantof the material I8V are such. as. to secure forv guide 23;. a phasev velocitywhich, for a given:slotispacing,.causesmaxifmumA radiation and reception to.. occur at:v an angle of +0 or -0 relative to the broadside*v direction 0:0. TheV broadside vdirectionf is perpendicular to the guide axis 24 and the arrayv axisV 28.

In operation, referring to Figs. 1.. and. 2 and assuming device I is a transceiverand'theY deVv tuning-vane is continuously rotating about. axis I3, centimetric waves aresuppliedby thel transmitter in transceiver I over liner 2fto the. main guidegrand to the two apertures. I4l of the wave guide switch 1; The vane IZ alternately detunes chambers 9 and I0 and theenergy flowsat anyv given instant through.- only one ofv these timed cavities. Hence the waves are supplied alter-- nately to sectionsIQ'of `guides I6' and'l'l throughy apertures 2l, as. indicatedl by' the full-line and dotted line arrows 33 and 34.` Considering the waves established in branch guide. I5' and"V having propagation direction 33, the energy. flows.

from section I9 into section 20 and enters the wave guide antenna 23 at point 29. In guide 23 the waves reflected by end wall 30 and traveling in direction 33 combine in phase with the waves propagated in direction 33 directly from point 29 toward the center of array 21. The energy is emitted through the slot antennas 26 and maximum radiation occurs in the -0 direction which forms with direction 33 an obtuse angle. Since, as disclosed in the Southworth application, for a polystyrene loaded leaky Wave guide ot the. second kind, broadside operation is secured with a slot spacing of a wavelength as measuredY in. the guide, corresponding to 0.6 to 028 of'a wavelength as measured in the air, the slot spacing should be greater than 0.6 to 0.8 of afwavelength. as measured in the air, yfor lobe switching operation. In a similar manner the Vwaves alternately supplied to branch guide I1 enter guide 23 at point 3| and have in antenna guide 23l a direction 34. opposite direction. 33 wherebyA maximum radiation is; secured in. av

direction +0- which forms with direction '34.r anobtuse angle.

Assuming echo pulses are returned. to array 2l by reilective objects, theA reciprocal operation is obtained, the receiving pulses being conducted to thev receiver in transceiver I alternately via branch guides I3 and I'I- by reason of. the rotation. of vane I2 in switch 1. Hence; in. accordance with the invention, the' centimetric array 21 is, in the case of transmitting, fed al` ternately at opposite ends of. guide'23. and, in theV case of reception, the opposite ends are con vnected alternately to the receiver, whereby as illustrated by Fig. 2 the maximum transmitting and the Imaximum receiving lobe are. each switched back and forth Vbetween the positions:

denoted by numeral 35 and numeral 36. Lobes'Y 35j and 36 are the so-cal-led resultant lobesobtained by multiplying thefma-ximum. array lobe.

and the typical maximumlobe. for each unit antenna.: or aperture 2.6. Asin conventional lobev switchingY systems, if. avparticular target is oI the 0;-:0 direction, the echo pulses received. from. theftarget forthe two lobe.v positions are unequal.

in magnitude, whereas if. the target is located.

on the 0:0- direction the aforementionedv echo pulses have equal intensities. Stated differ.-

, ently, the lineV or direction, 0=0r is the so-called 24 angularly related.4 The; two. guides. 23 make equal and opposite anglesv with; the; direction'.

a=0 which is perpendicular4 to thebisector 38 or the .bisecting plane of the dihedral angle Aiormed. by the front walls ofY the.- two guides` 23. TheY upper andlower guides' 23:.contain, respectively,

the` arrays 39 and 40, eaclr identical to the array 27 of Fig. l. The upper wave guide 23? is=con nected at a point adjacent itsfar end to one branch coaxial line 4I and the lower wave guide 23 is connected at a point adjacent itsnearend to another branch coaxial line 4I, that is. theguides 23 are connected to the branch lines 4! at points near the uncorrespondent ends of the guides. Each of lines 4l is connected to a sepan rate air-filled branch wave guide 02, and the two branch guides 42 are connected through a wave guide switch l, main guide 5 and main line 2 to the translation device l In operation, pulsed centimetric waves are supplied alternately through wave guide switch l' to the two arrays 39 and 49 and the echo pulses are received alternately by the two arrays. Since the two guides 23 have the same slot spacings and equal phase velocities, and are energized at uncorrespondent ends, the directions of maximum action for the arays 39 and 40 make equal opposite angles with the direction az. More specically, the array 39 of the upper guide 23 has a direction 030 of maximum transmitting and receiving action and the array 40 of the lower guide 23 has a direction +040 of maximum action, the broadside directions 030:0 degrees and 040:0 degrees being perpendicular to the axes 24 of the arrays 39 and 40, respectively. The direc tion 0:0 corresponds to the equal intensity path and, as vane l 2 of switch i rotates, switching between the lobes of the two arrays is secured. In Fig. 2, diagrams 35 and 33 may be taken to represent the resultant lobes for the arrays 39 and 40. The angle between the arrays 39 and 40 may, if desired, be adjusted by rotating either or both guides 23 about axis 43.

The system of Fig. 4 is the same as that illustrated by Fig. 3, except that the branch coaxial lines 4| are connected to points in guides 23 adjacent correspondent ends of the guides. As indicated by the lines X-X, Figs. 3 and 4, the system of Fig. 4 includes the equipment shown below line X-X in Fig. 3, the branch lines 4l in Fig. 4 being connected, as in Fig. 3, to branch guides 42, wave guide switch 1, guide 5, line 2 and translation device I.

The operation of the system of Fig. 4 is believed to be apparent in View of the explanation given above. As in the system of Fig. 3, switch 1 functions to connect the device I alternately to the two guides 23 for lobe switching operation. The angle between the axis 24 of array 39 and its direction +039 of maximum action is equal in degree to, and in contradistinction to the system of Fig. 3, is of the same sense as, the angle between axis 24 of array 40 and its direction +040 of maximum action. Since the axes 24 are angularly related the directions +030 and +040 are angularly related, and the line of equal intensity is the bisector of the angle formed by the directions +039 and +040. The equal intensity line is angularly related to the direction a=0, which is perpendicular to the bisector 38 of the angle A between the guides 23, whereas in the system of Fig. 3 the equal intensity line and the direction =0 are superposed.

Although the invention has been explained in connection with certain embodiments, it should be understood that it is not to be limited to the embodiments described, inasmuch as other apparatus may be successfully employed in practicing the invention.

What is claimed is:

1. In combination, a pair of angularly related rectangular linear wave guides each having in one magnetic plane wall an antenna array comprising a plurality of spaced antenna apertures, a translation device, and means for alternately connecting said device to said guides at points adjacent the opposite guide ends, each array having a direction of maximum action angularly related to its respective guide wall.

2. In combination, a lobe switching antenna array comprising a pair of angularly related superposed rectangular wave guides, a translation device, means for alternately connecting said device to one guide near one end and to the other guide near the uncorrespondent end, each of one pair of similar guide walls containing an antenna subarray comprising a plurality 0i spaced apertures, the directions of maximum action for said subarrays making equal and opposite angles with the bisector of the angle between said similar walls.

3. In combination, a lobe switching antenna system comprising a pair of angularly related superposed rectangular metallic wave guides each iilled with polystyrene, a translation device, means for alternately connecting said device to one guide near one end and to the other guide near the correspondent end, each of one pair of similar guide walls containing an antenna subarray comprising a plurality oi spaced apertures, the directions of maximum action for said subarrays making unequal angles with the bisector of the angle between said similar walls.

4. In combination, an antenna system comprising at least one linear dielectric guide containing a solid dielectric substance, said guide having a plurality of transverse slots for radiating or collecting radio energy, a pair of branch dielectric guides connected to spaced points in said system, a translation device, a main dielectric guide, a coaxial line connecting said device to said main guide, and a wave guide switch comprising a pair of dielectric chambers and a rotatable element for alternately tuning and detuning said chambers, said main guide being connected to one branch guide through one of said cham.- bers and to the other branch guide through the remaining chamber.

CARL B. H. FELDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS' Number Name Date 2,206,923 Southworth July 9, 1940 2,241,119 Dallenbach May 6, 1941 2,256,090 Illberg et al Sept. 16, 1941 2,281,274 Dallenbach et al. Apr. 28, 1942 2,349,942 Dallenbach May 30, 1944 2,402,622 Hansen June 25, 1946 2,405,242 Southworth Aug. 6, 1946 2,408,425 Jenks et al Oct. 1, 1946 2,408,435 Mason Oct. 1, 1946 2,414,791 Barrow Jan. 28, 1947 FOREIGN PATENTS Number Country Date 833,529 France July 25, 1938 

